Light can be represented as electromagnetic fields which vary sinusoidally and orthogonal to the direction of propagation as shown in FIG. 1. [where the direction of propagation is along the Z-axis.] In FIG. 1 the electric field component of the wave is denoted by E, and the magnetic field component is denoted by B.
For the purposes of this invention it is only the electric field component of the wave which will interact with matter and produce relevant phenomena. An electric field is simply the force per unit electric charge in a region of space. Equivalently, if an electric charge were in a region of space occupied by an electric field it would experience a force equal to the electric field times the magnitude of the charge.
Electric fields can be represented mathematically as vector quantities indicating their magnitude and direction at a specific point or in a given region of space. FIG. 1A is the electromagnetic wave in FIG. 1, but with the view looking down the axis of propagation, the Z-axis. FIG. 1-A shows some possible orientations of the electric field. These are only some possibilities. Any orientation in the plane normal to the direction of propagation is possible. That plane is represented as the plane that the circle in FIG. 1A occupies.
As light, an electromagnetic wave, propagates, the behavior of the electric field in space and time is determined by Maxwell's equations, which are a set of equations defined by James Clerk Maxwell which constitute the physical laws of electromagnetism. Maxwell's equations have solutions for travelling waves where the electric field varies along an axis as in FIG. 1, varies in a circular of elliptical manner, or varies randomly.
The orientation of the electric field vector and how it changes with time is known as the state of polarization of the electromagnetic wave or just simply the polarization of the light. If the electric field is confined to a single axis as in FIG. 1 it is said to be linearly polarized. In FIG. 1 it is linearly polarized in the X or vertical direction. Since the electric field at any given moment is confined to a plane parallel to the direction of propagation and a plane is two dimensional, there are only two possible independent polarization states for light. We can think of them as horizontal and vertical. Although in physics and mathematics the two unique polarization states used are sometimes right and left circular polarization, these states are simply combinations of vertical and horizontal states that vary in time in the right way to represent an electric field that rotates in a circular clockwise manner or counterclockwise as the wave propagates. The specific time relationship between the vertical and horizontal states is called a phase relationship.
If the electric field in FIG. 1 is not confined to a single axis in the plane but has an equal probability of being in the horizontal or vertical direction and there is no specific phase relationship between the vertical and horizontal electric fields the light is said to be unpolarized or randomly polarized.
The electric field can be polarized and confined to an axis that makes and angle, .theta., with the horizontal or x-axis as shown in FIG. 1B. Since the electric field is a vector quantity when it is polarized in this manner, it can be broken up into horizontal and vertical components. In FIG. 1B the horizontal axis is the x-axis and the vertical axis is the y-axis. The electric field E in FIG. 1B has a horizontal component equal to E cos .theta. and a vertical component equal to E sin .theta., this being a trigonometric fact. It can be said that the electric field in FIG. 1B has a part of itself, E cos .theta., polarized along the x-axis and the rest of itself E sin .theta., polarized along the y-axis. The sides of the triangle in FIG. 1B formed by E, E cos .theta., and E sin .theta. obey the pythagorean theorem, which means they obey the relations E.sup.2 cos.sup.2 +E.sup.2 sin.sup.2 .theta.=E.sup.2. For the purposes of our discussion it must be understood that the electric field E has a component E cos .theta. polarized in the x-direction and a component E sin .theta. polarized in the y-direction.
Some materials act as polarizers. If randomly polarized light enters into a slab of finite thickness of polarizing material with the material's polarization oriented say in the vertical direction, the horizontally polarized portion of the incident light is absorbed and the vertically polarized portion is allowed to pass through the material. The result is that the light emanating out of the polarizing material is polarized in the vertical direction thus polarizing materials polarize light.
One can think of polarizers as having a transmission axis or sense and an absorption axis or sense. It is more general to use the word sense than axis since axis implies the idea of linearity to the imagination of the reader and that does not apply to circular polarizers and so can become confusing when one is trying to provide broad and general clarity.
If linearly polarized light oriented in the vertical direction enters a linear polarizer whose absorption sense is oriented in the vertical direction the light will be absorbed. Equivalently, if linearly polarized light is projected onto a polarizer whose absorption sense is equal to the polarization sense of the light, the light is absorbed. If linearly polarized light is projected onto a polarizer whose absorption sense is orthogonal to the polarization sense of the light, the light is transmitted.
The same statements of what happens physically can be made using reference to the transmission sense of the polarizer. For instance, if linearly polarized light is projected onto a polarizer whose transmission sense is equal to the polarization sense of the light the light is transmitted. If linearly polarized light is projected onto a polarizer whose transmission sense is orthogonal to the polarization sense of the light, the light is absorbed.
Circular polarizers have an absorption sense and a transmission sense as well. The above reasoning carries through for circular polarizers and circularly polarized light. For instance if circularly polarized light is projected onto a circular polarizer with an absorption sense equal to the polarization sense of the light, the light is absorbed. If the absorption sense of a circular polarizer is left, left circularly polarized light is absorbed when projected onto the polarizer etc.
To expand our vocabulary to encompass an understanding of the relationship between linear polarization (of light or materials), circular polarization (of light or materials), and light that is unpolarized the following facts must be rigorously observed.
(1) Unpolarized light can be represented as an equal mixture of horizontal linearly polarized light and vertical linearly polarized light, where the phase relationship between the vertical and horizontal linearly polarized states is random.
(2) Unpolarized light can also be represented as an equal mixture of right circularly polarized light and left circularly polarized light, where the phase relationship between the right and left circularly polarized states is random.
(3) Linearly (horizontal or vertical) polarized light can be represented as a linear combination of right and left circularly polarized light, where the phase relationships between the right and left circularly polarized states is specific.
(4) Circularly (right or left) polarized light can be represented as a linear combination of horizontal and vertical linearly polarized light, where the phase relationship between the horizontal and vertical linearly polarized states is specific.
The above facts can be derived from Maxwell's equations or from the quantum mechanical theory of light. Both methods produce the same results. Further the above facts have been verified by experiment with great rigor.
For the purposes of this invention the phase relationship in facts (3) and (4) does not have any physical optical consequences. So we can think of linearly polarized light as an equal amount of right and left circularly polarized light; and we can think of circularly polarized light as an equal amount of horizontal and vertical linearly polarized light.
If circularly polarized light is projected onto a linear polarizer the part of the light that has a polarization sense equal to the transmission sense of the polarizer is transmitted and the other part has a polarization sense equal to the absorption sense of the polarizer and is absorbed. The same holds for linearly polarized light projected on to a circular polarizer.
The interrelationships between linearly and circularly polarized light and linear and circular polarizers relate to this invention.
Some linear polarizers are composed of metal crystals aligned along a specific direction. These are also called metal polarizers. Metal polarizers do not have an absorption sense but have instead a reflection sense. The orthogonal sense to their reflection sense is their transmission sense. Metal polarizers relate to some aspects of this invention.
The making of sheet polarizers, polarizing material on large sheets of substrates, was pioneered by Edwin H. Land and more by John F. Dreyer. The polarizing layer on these substrates is called a dichroic layer. The phenomena of polarizers and polarizing sheets relate to this invention.
There are also techniques of depositing thin layers of metal, metal oxides, or conducting polymer materials onto substrates. These layers do not polarize light but they act as partial reflectors. They reflect only part of the light that is shined upon them. When you look at one of these layers on a clear substrate you can see objects on the other side and you can also see your reflection. As the thickness of these layers is increased the reflective property increases and the transparent property decreases. The phenomena of partial reflection relates to this invention.
Polarizing layers and partially reflective layers can be combined as parallel elements onto substrates to produce laminates that can be used for various purposes. Various prior art techniques have been developed to produce such combinations of parallel elements for various purposes. See U.S. Pat. No. 2,776,598 to Dreyer, U.S. Pat. Nos. 2,788,707 and 2,997,390 to Land, U.S. Pat. No. 4,025,688 to Nagy et al., U.S. Pat. No. 5,347,644 to Sedlmayr et al., and U.S. Pat. No. 3,248,165 to Marks, et al.
Other materials are largely transmissive, meaning their reflecting qualities are minimal. That is to say when one shines light on them the majority of it goes through then without being reflected or absorbed. Transparent and transmissive materials relate to this invention.
Other materials are partially transparent and diffusive. Diffusive means that they scatter light in many directions. Intrinsically, this diffusive quality is due to natural perturbations in the index of refraction. Extrinsically the diffusive quality is due to pores, grain boundary defects, strain fields, small quantities of particulate matter, and crystallographic defects. Optical materials are generally made to minimize the diffusive quality but in some designs of the proposed invention it is actually desirable to have a partial diffusiveness. Candidate materials that have a partial diffusiveness include; alkali and alkaline earth halides such as chlorides, bromides, iodies, B.sub.a F.sub.2, P.sub.b F.sub.2 ; oxides such as Al.sub.2 O.sub.3 ; oxynitrides such as ALON; chalcogenides such as ZnSe and ZnS; and semiconductors such as Si, Ge, and Go,As. The extrinsic diffusiveness can be adjusted depending on how the materials are made. For more details see, Optical Materials, Ed Solomon Musikant; Marcel Dekker, Inc. 270 Madison N.Y., N.Y. 10016. The partial transparency is a achieved by using only a thin layer of such materials.
This invention employs combinations of polarizing, reflective, diffusive and transmissive parallel elements combined on an optical substrate of specific design parameters, governed by the operation of the invention. Also this invention claims a new application for sheet polarizers in general and the novelty of that application dictates specific structural and dimensional parameters for such sheet polarizers.
Various prior art techniques and apparatus have been heretofore proposed to present three dimensional images on a viewing screen using a stereographic technique such as on a polarization conserving motion picture screen.
See U.S. Pat. No. 4,955,718 to Jachimowicz, et al., U.S. Pat. No. 4,963,959 to Drew, U.S. Pat. No. 4,962,422 to Ohtomo, et al., U.S. Pat. No. 4,959,641 to Bess, et al., U.S. Pat. No. 4,957,351 to Shioji, U.S. Pat. No. 4,954,890 to Park, U.S. Pat. No. 4,945,408 to Medina, U.S. Pat. No. 4,936,658 to Tanaka, et al., U.S. Pat. No. 4,933,755 to Dahl, U.S. Pat. No. 4,922,336 to Morton, U.S. Pat. No. 4,907,860 to Noble, U.S. Pat. No. 4,877,307 to Kalmanash, U.S. Pat. No. 4,872,750 to Morishita, U.S. Pat. No. a4,853,764 to Sutter, U.S. Pat. No. 4,851,901 to Iwasaki, U.S. Pat. No. 4,834,473 to Keyes, et al., U.S. Pat. No. 4,807,024 to McLaurin, et al., U.S. Pat. No. 4,799,763 to Davis, U.S. Pat. No. 4,772,943 to Nakagawa, U.S. Pat. No. 4,736,246 to Nishikawa, U.S. Pat. No. 4,649,425 to Pund, U.S. Pat. No. 4,641,178 to Street, U.S. Pat. No. 4,541,007 to Nagata, U.S. Pat. No. 4,523,226 to Lipton, et al., U.S. Pat. No. 4,376,950 to Brown, et al., U.S. Pat. No. 4,323,920 to Collendar, U.S. Pat. No. 4,295,153 to Gibson, U.S. Pat No. 4,151,549 to Pautzc, U.S. Pat. No. 3,697,675 to Beard, et al.
These techniques and apparatus involve the display of polarized or color sequential two-dimensional images which contain corresponding right eye and left eye perspective views of three dimensional objects. These separate images can also be displayed simultaneously in different polarizations or colors. Suitable eyewear, such as glasses having different polarizing or color separations coatings permit the separate images to be seen by one or the other eye. This type of system is expensive and cumbersome because it requires collecting the image from two different views which demands a special camera or two cameras.
U.S. Pat. No. 4,954,890 to Park discloses a representative projector system employing the technique of alternating polarization.
Another technique involves a timed sequence in which images corresponding to right-eye and left-eye perspectives are presented in timed sequence with the use of electronic light valves. U.S. Pat. No. 4,970,486 to Nakagawa, et al., and U.S. Pat. No. 4,877,307 to Kalmanash disclose representative prior art of this type. This time sequence technique also requires the use of eyewear.
There is another example of the timed sequence technique in which the left and right eye views have different polarizations and are viewed not with glasses but with a single polarized screen over both eyes. The screen is formed of a transparent material that has two or more different specialty coatings. U.S. Pat. No. 5,347,644 to Sedlmayr discloses representative prior art of this type.
The timed sequence also requires collecting the image from different views, right eye and left eye.
Alternating polarization and timed sequence stereoscopic techniques both possess the following disadvantages; the image cannot be collected or displayed with convention single view equipment, and eyewear is required for viewing.
U.S. Pat. No. 5,543,964 to Taylor et al. is another example of superimposing images to create an illusion of depth based on the stereo nature of human vision. The proposed invention creates depth using a single image and is not based on binocular vision. Another superimposition technique is shown in U.S. Pat. No. 5,556,184 to Nader-Esfahani. Again the proposed invention is not based on superimposition of images. U.S. Pat. No. 5,589,980 to Bass displays images in apparent three dimensions using two display devices, one being in front of the other creating apparent depth. The proposed invention displays images in apparent three dimensions using a single screen instead of two.
U.S. Pat. No. 5,559,632 to Lawrence et al. introduces special glasses for viewing regular images in apparent three dimensions employing stereoscopic theory. The proposed invention is not based on stereoscopic theory, and does not require eywear.
It is known that holographic techniques have been used for three dimensional information recording and display. These techniques involve illuminating a three dimensional object with a coherent (laser) beam of light and interfering that light with a reference beam from the same source. The interference pattern is collected on a recording film medium and illumined with the same coherent light from which it was made. The result is a projected image of the object in three dimensions able to be viewed without eyewear. Holographic techniques are not in general use because inherent in them are many limitations: an object has its dimension limited to an extent that it can be illuminated by a laser beam; the object should be stationary; a photograph thereof must be taken in a dark room; and the image cannot be collected and displayed in real time.
Some of the limitations of holography have been addressed by a technique known as composite holography.
Composite holography consists of photographing a three dimensional object in a plurality of different directions under usual illumination such as natural light to prepare a plurality of photographic film sections on which two-dimensional pictorial information is recorded. These two dimensional photographs are information images and are separately illumined with coherent (laser) light and are recorded as holograms. These holograms are then simultaneously illumined with coherent (laser) light producing a projection of the perspective information of the three-dimensional object to be recognized by unaided human eyes at different angles depending upon their position with as much effect as one substantially views the image of the three dimensional object.
Composite holography was limited since the size of the recording medium of the holograms had to be large leading to a large sized overall device making it economically impractical. That limitation was resolved by Takeda et al. as disclosed in U.S. Pat. No. 4,037,919. Also in that disclosure is a detailed description of composite holography.
The disadvantage of composite holography is that it involves photographing the object from many different angles and making a hologram of each of those photographic images. This makes it impossible to collect and display the three dimensional image in real time. A further disadvantage is that it is time consuming, laborious and expensive.
Another example of prior art includes a dual screen system composed of foreground and background screens. The images are collected and projected with incoherent white light. This dual screen system is disclosed in U.S. Pat. No. 3,248,165 to Marks et al.
Referring to FIG. 2 Marks' invention includes two projectors 30 and 31 for projecting two beams of light towards a multiple screen 32. A polarizing filter 33 polarizes the light from projector 30, so that the beam is polarized in the vertical direction as shown by arrow 34. Projector 31 directs its beam of light through a polarizing filter 35 so that the beam which is directed toward the screen arrangement is polarized in a horizontal direction as indicated by arrow 36.
FIGS. 2A, 2B, and 2C illustrate the manner in which the two screens are formed. The foreground screen 37 is formed with a plurality of holes 38 cut in the screen in a symmetrical array.
In the embodiment of FIG. 2D the solid part of the foreground screen is made up of three layers and includes a supporting sheet 39 which is made of some transparent plastic material. On the side facing the projectors, a thin polarizing film 40 is secured for passing rays of light polarized in the direction passed by the polarizing filter having a parallel plane of polarization and for absorbing the rays polarized at right angles thereto. On the back of the sheet 39 a diffuser-reflector film 41 is secured for reflecting the light rays in a diffused manner without changing their plane of polarization. This diffused reflector film is comprised of small aluminum flakes dispersed in a binder. Behind the diffuser-reflector film is a black coating.
The background screen 42 is composed of the same films and layers as the foreground screen 37 except no holes are cut in this screen and the plane of polarization of the polarizing film 40A is at right angles to the polarizing plane of film 40. In the example shown this plane is horizontal.
FIG. 2D illustrates the method in which the two screens cooperate with the two projectors. The two arrows 43 designate rays of two beams of vertically polarized light, one of which strikes a portion of the foreground screen 37 and also rays of two beams 44 polarized in a horizontal direction, one of said rays being directed through a hole 38 in the foreground screen and incident upon the background screen 42. One of the rays 43A from the projector 30 strikes a portion of the foreground screen and penetrates the polarizing film 40, the plastic film 39, and is diffusely reflected by the reflecting sheet 41. The polarizing film 40 is arranged for passing light which is vertically polarized.
A second ray of light 43B from projector 30 passes through one of the holes 38 and is incident upon a polarizing film 40A on the rear screen 42 which is arranged to pass light which is polarized only in the horizontal direction. For this reason light ray 43B is absorbed in film 40A and cannot be seen by the audience. In a like manner, a ray of light 44A, polarized horizontally, strikes polarizing film 40 and is absorbed while another ray 44B from this same projector passes through hole 38, strikes polarizing film 40A, and is transmitted to the diffusing reflecting sheet 41. The reflected light rays 45 are directed toward the audience but only a portion of them pass through holes 38.
It will be obvious from the above description that one portion of the picture will be projected to the background screen 42, where it will be viewed by the audience while another portion of the picture is projected onto the foreground screen 37 where it also will be seen by the audience. In general, the background picture will contain objects that are generally parts of a background such as a distant set of objects or a portion of a room or other enclosure which forms the background of a scene. The foreground screen generally will show the actors or other moving objects which are generally desired to be shown in a position which is closer to the audience.
The background screen is on a mechanical motor driven track which enables its distance from the foreground screen to be adjusted.
Marks' dual screen system requires two projectors, one for the foreground image and one for the background image. This is a disadvantage because it is desirable to project the image with conventional single projection equipment so that the extra cost involved in equipping a theatre or home entertainment unit is minimal. It will become obvious that the proposed invention produces a three-dimensional image with a single conventional projection unit.
Marks' system requires two screens to produce apparent depth, a foreground and a background screen. The proposed invention produces apparent depth with a single screen.
Marks' system produces an image with an apparent three dimensional quality of an entire landscape that includes actors and foreground objects on the foreground screen and scenery and background objects on the background screen. The foreground screen is partially transparent because it has holes in it This partial transparency of the foreground screen gives rise to the apparent depth between the foreground and background. The solid part of the foreground screen and the entire background screen are both opaque to the naked eye. The partial transparency of the foreground screen is, again, due to actual physical holes. If the system were displaying a static scene on the background screen and a moving person or object on the foreground screen and a viewer were looking at the image of person or object on the foreground screen from say, ten feet away, the viewer would see holes in the image of the person or object on the foreground screen and the image would not look real. A disadvantage of this system is that it cannot display a performer on a stage in a small theatre or barroom because the audience is too close and the holes in the screen will be seen. This disadvantage also disqualifies this system to be a small home display where a life size three dimensional display of a person could be used for a video phone display or a computer or television display since the viewer would only be several feet from the screen, and again the holes would be visible.
Dual polarizing reflection filter is another technique of producing on three dimension image and was introduced by myself as disclosed in U.S. Pat. No. 5,469,295. This technique involves projecting an image with polarized light onto a sheet polarizing, partially reflective screen whose polarization sense if orthogonal to that of the projected light. Thus the isolated projected image is stopped completely on the partially transparent screen. I shall refer to U.S. Pat. No. 5,469,295, as the Burke I system.
FIG. 3 shows a perspective view of the basic embodiments of the Burke I system which a projector which projects an image with polarized light 102, a real physical three dimensional object 103A a projected image 105, a partially reflective and transparent sheet polarizing screen 104 of the opposite polarization sense to that of the polarizer 102 and a real physical three dimensional object 103B.
The screen 104 consists of several layers and a perspective view of the cross section of a first design for the screen is shown in FIG. 5.
The screen consists of a transparent substrate 108, a polarizing layer 109, a binding layer 110, another transparent substrate 111A, and a partially reflective and transparent layer 111B.
A perspective view of the cross section of a second design for the screen of the Burke I system is shown in FIG. 6. The screen consists of a transparent substrate 112A, a polarizing layer 113, a transparent binding layer 114A, a transparent substrate 115A, a partially reflective and transparent layer 115B, a transparent binding layer 114B, and a transparent substrate 112B. In both screens proposed the partially reflective and transparent layer is closest to the projector and the polarizing layer is behind the partially reflective and transparent layer and is thus farther from the projector.
In both screens the transparent substrates must be made of materials that do not change the state of polarization of light when it passes through them.
The transparent substrates 108, 111A, 112A, 112B, and 115A, are clear glass or plastic. 108, 112A, and 112B are thick enough so that the screen has mechanical stability for a given size of viewing area. 111A and 115A are only thick enough so the partially reflective and transparent layer can be bound to the polarizing layer.
The polarizing layers 109 and 113 are of an orthogonal polarization sense to that of the projected light.
The reference objects 103A, 103B are real physical three dimensional objects placed in front of and behind the screen.
Referring to FIGS. 3 and 4; the projector 102, projects the isolated image with polarized light in the frame 106 and does not project the surrounding background in the frame 107 because it is opaque.
The polarized projected image moves through the air until it hits the partially reflective and transparent sheet polarizing screen 104 where it is stopped, reflected and seen on the screen as a solid image.
Referring now to FIG. 7, the polarized light carrying the image is represented diagrammatically as a wave 115. The partially reflective and transparent sheet polarizing screen, though it is many layers, is represented schematically in FIG. 7 as two layers, a partially reflective and transparent layer 119, and a polarizing layer 120.
When the polarized projected wave 115 hits the partially reflective and transparent layer 119; part of it is a reflected wave 116 and is seen by the audience as the image of the subject on the screen; part of it is a transmitted wave 117 and moves through the partially reflective and transparent layer 119. The transmitted wave 117 moves into the polarizer 120 and becomes an absorbed wave 118 as the polarizer absorbs and diminishes its amplitude to zero. The polarizing material must be thick enough so that the wave 118 decays to zero while it is in the polarizer 120. This insures that none of the projected light passes through the screen since that which is not reflected is absorbed.
The wave that is transmitted 117 through the partially reflective and transparent layer 119 must not have its polarization changed as it passes through the material 119 since the reason it is absorbed by the polarizer 120 is because it has a polarization sense orthogonal to the polarizing material. Equivalently if the projected wave has a vertical polarization the sheet polarizer has a horizontal polarization sense and vice versa.
The viewer sees by way of unpolarized light since there is no eyewear required and his or her perception is accomplished with the naked eye. Since unpolarized light is an equal amount of vertically and horizontally polarized light we can examine the path of sight of the view by examining the interaction of each polarized state of light with the screen.
The light by which the viewer sees that is polarized orthogonal to the polarization sense of the polarizer 120 in the screen can be represented diagrammatically by the wave 126 in FIG. 7. The wave 126 hits the screen's partially reflective and transparent layer 119 and part of it is a reflected wave 127 which is small in amplitude compared to the reflected wave 116 and is relatively unseen. Part of the wave 126 becomes a transmitted wave 128 and passes through the partially reflective and transparent layer 119 and moves into the polarizing layer 120 and becomes an absorbed wave 129 and decays to zero in the polarizer.
The light by which the viewer sees that is polarized parallel to the polarization sense of the polarizer 120 in the screen can be represented diagrammatically by the wave 121 in FIG. 7. The wave 121 hits the screen's partially reflective and transparent layer 119 and part of it is a reflected wave 122 which is small in amplitude compared to the reflected wave 116 and is relatively unseen. Part of the wave 121 becomes a transmitted wave 123 and passes through partially reflective and transparent layer 119 and into the polarizing layer 120 where the transmitted wave is referred to as 124. The wave 124 is polarized parallel to the polarization sense of the polarizer 120 in the screen and therefore the wave 124 passes through the polarizer and emerges as wave 125 on the other side of the screen. The wave 121 which becomes waves 123, 124, and 125 and thus passes through the screen is the means by which the viewer sees through the screen and represents the transparent quality of the screen.
Since the reflected wave 116 is much higher in amplitude than the transmitted wave 125 the image of the object or person on the screen which is represented by the wave 116, does not appear to be transparent to the viewer but looks solid.
The light emanating from the reference object that is polarized orthogonal to the polarization sense of the screen is represented by the wave 131 in FIG. 7. Wave 131 propagates toward the screen until it hits it and moves into the polarizing layer 120 and becomes an absorbed wave 132 and decays to zero.
The light emanating from the reference object that is polarized parallel to the polarization sense of the screen is represented by the wave 133. Wave 133 hits the screen and moves into the polarizer and becomes a transmitted wave 134. The transmitted wave 134 moves through the polarizer and hits the partially reflective and transparent layer where part of it becomes a reflective wave 135 and part of it becomes a transmitted wave 136.
The reflected wave 135 moves back into the area behind the screen where it can be absorbed either by an optical absorber or it can travel into abeyance if there is enough space behind the screen.
The transmitted wave 136 moves through the partially reflective layer 119 and on out into the area in front of the screen and is referred to as wave 137 in FIG. 7.
Wave 137 carries with it the image of the reference object and is seen by the viewer. Thus again we see that objects behind the screen are visible to the viewer.
Referring now to FIG. 3 the projected image is stopped by and reflected off of the screen and is seen as a solid isolated figure 105 on a partially reflective and transparent screen 104 with no holes in it.
The isolated image of the subject 105 on the partially reflective and transparent screen 104, in the presence of reference objects 103A and 103B, appears to be three dimensional when viewed by a viewer positioned at any point in front of the screen.
One disadvantage of the Burke I system is that the partially reflective layer is on a substrate which is glued to the polarizing layer when, for simplifying manufacturing, the reflective layer can be bonded directly to the polarizing layer eliminating the need for a substrate and a binding layer. The reflective layer could be a clear polyurethane paint for instance, which has reflective properties and sticks directly to the polarizing layer.
Another disadvantage of the Burke I system is the reflective layer is a separate layer than it could be eliminated by using a polarizer which has reflective properties, thus again simplifying the manufacturing of the system.
Another disadvantage of the Burke I system is that it cannot be structured as a rear projection system, which for some commercial products is more desirable or is required.
Another disadvantage of the Burke I system is that the image can only be viewed from the area in front of the screen which means the area behind the screen is wasted real estate. For entertainment units in restaurants and bars it would be ideal to be able to see the image from either side of the screen.
Another disadvantage of the Burke I system is that it requires the projected image to be projected with fully polarized light. If one wants to use a projector with unpolarized light the light has to be polarized as it comes out the front of the projector and the projected image loses half of its brightness, if the light is polarized using a filter.
The proposed invention includes a bead layer or a diffusive layer. This layer has specific microstructure. The beads are of specific sizes. The diffusive layer has particles in it of specific dimension if it is an extrinsic diffusive material. If it is an intrinsically diffusive material its index of refraction varies periodically in space with specific dimension. This specific dimension is on the order of the size of the wavelengths of projected light. This feature adds depth to the image and is absent in the Burke I System.
The proposed invention also makes use of optical surface area. This is discussed later in this section and again in the section on theory. This feature further increases the depth of the image and is absent in the Burke I System.
The proposed invention is different than the burke I system in the structure and dimension of the screen and the polarization content of the projected light Further the proposed invention produces three dimensional images of entire scenes.